JPS6312464A - Transparent laminated plastic film having excellent gas barrier property - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transparent laminated plastic film with excellent gas barrier properties that is used as a packaging material for foods, medicines, chemicals, and the like.

"Prior Art" Generally, plastic films used as packaging materials for foods, medicines, chemicals, etc. are made of so-called gas barrier properties, which have low permeability to gases such as water vapor and oxygen, in order to prevent deterioration of the packaged contents. Excellent materials are used. When even higher gas barrier properties are required, aluminum foil has been pasted onto a plastic film, or aluminum has been vapor-deposited on the surface of the plastic film.

However, packaging materials using such metal foil are
Although it has excellent gas barrier properties against water vapor and oxygen, it has the major drawback of not being able to see the contents from the outside because it is opaque, making it undesirable as a packaging material.

In addition, polyvinylidene chloride and vinylidene chloride, such as copolymers with vinylidene chloride and compounds copolymerizable with vinylidene chloride, such as vinyl chloride, methyl acrylate, methyl methacrylate, acrylonitrile, etc., are also used as packaging materials with gas barrier properties. Vinylidene chloride resin films and vinylidene chloride resin coated films, which are films made of polypropylene, polyester, polyamide, etc., coated with copolymers of these resins are also used.

However, although these vinylidene chloride resin films have gas barrier properties against water vapor and oxygen, they are not sufficient and are unsuitable for use as packaging materials that require a high degree of gas barrier property. Ta.

On the other hand, polyvinyl alcohol films and polyvinyl alcohol films such as ethylene-vinyl alcohol copolymer films have excellent oxygen barrier properties and are therefore widely used as packaging materials. However, this polyvinyl alcohol film has the disadvantage that it does not have sufficient water vapor barrier properties, and also has the disadvantage that its oxygen barrier properties deteriorate under conditions of high humidity.

Therefore, when polyvinyl alcohol film is used as a packaging material, polypropylene film, polyethylene film,
It is commonly used as a laminated film made by laminating films having water vapor barrier properties such as polyester films. However, such laminated films are not fully satisfactory as packaging materials that require high gas barrier properties. Further, although such a laminated film has improved oxygen barrier properties to some extent under high humidity conditions, it is still not sufficient at present.

A known method is to increase the thickness of the laminated film in order to improve the elasticity of the laminated film, but when this method is used, the transparency and flexibility of the laminated film are lost and the packaging material The aptitude necessary for this will be lost.

[Problems and Points to be Solved by the Invention] The present invention aims to provide a plastic film laminate that is suitable as a packaging material for foods, medicines, chemicals, etc., that is, has excellent gas barrier properties and is transparent. be.

"Means for Solving the Problem" The gist of the present invention is to modify at least one side of a polyvinyl alcohol-based plastic film containing 50 mol% or more of polyvinyl alcohol with an acyl chloride compound. After that, a transparent plastic film other than the above-mentioned film is laminated on both sides of the above-mentioned film.

The present invention will be explained in detail below.

The transparent laminated plastic film with excellent gas barrier properties according to the present invention has a polyvinyl alcohol plastic film disposed in the center layer, and different types of transparent plastic films are laminated on both sides of the polyvinyl alcohol plastic film.

In the present invention, the polyvinyl alcohol film is
50 mol% or more of polyvinyl alcohol, preferably
A plastic film containing 70 mol% or more of polyvinyl alcohol. Specifically, polyvinyl alcohol obtained by saponifying polyvinyl acetate, ethylene-
A plastic containing 50 mol% or more of polyvinyl alcohol (preferably 70 mol% or more), such as an ethylene-vinyl alcohol copolymer obtained by saponifying a vinyl acetate copolymer, can be prepared by a known method, e.g. There are films formed by solution casting, extrusion, inflation, etc. These polyvinyl alcohol-based plastic films may be unstretched or -axially or biaxially stretched, but in order to exhibit high gas barrier properties, it is necessary to stretch them. preferable.

In the present invention, at least one side of the polyvinyl alcohol film is catalytically modified with an acyl chloride compound and then laminated with a different type of transparent plastic film.

In the present invention, the acyl chloride compound generally refers to a compound represented by the general formula RCOC+ (wherein R represents a monovalent organic group such as an alkyl group, a substituted alkyl group, or a phenyl group).

Examples of such acyl chloride compounds include acetyl chloride, propionyl chloride, butyryl chloride, pentanoyl chloride, hexamethyl chloride, octaphyl chloride, 7 nanoyl chloride, decamethyl chloride, benzoyl chloride,
Examples include phenylacetyl chloride, imbutyryl chloride, and inpentafil chloride.

The polyvinyl alcohol-based plastic film (
At least one side of the PVA film (hereinafter abbreviated as PVA film),
The above-mentioned acyl chloride compound can be contacted and modified by, for example, the following method.

That is, the acyl chloride to be used is heated in a boiling point I- under reduced pressure, and the generated acyl chloride vapor contains P.
A method of contacting and modifying the XI A film by exposing it to a so-called gas phase method, and adding a scavenger for free hydrochloric acid by reaction such as pyridine to the acyl chloride liquid used as necessary, and adding a scavenger of free hydrochloric acid by reaction such as pyridine to this For example, the method of immersing the liquid (immersion method). In these methods, for example, at a temperature of about room temperature to 100°C, the heating time is 10 minutes to 2 minutes.
It is enough to keep them in contact for about an hour. Here, if the contact time is too long, the PVA film may be deteriorated, which is not preferable.

PVA by contacting with acyl chloride compounds
The film surface is acylated and modified, but at this time PV
A film can be modified by contacting only one side or both sides. +71+ PVA after being brought into contact with an acyl chloride compound and modified.
The film is usually dried under reduced pressure by heating at a temperature higher than the boiling point of the acyl chloride compound used to remove the remaining acyl chloride compound.

In the laminated plastic film according to the present invention, a transparent plastic film other than the PVA film is laminated on both sides of the PVA film, which has been acylated on one or both sides.

However, when only one side of the PVA film is brought into contact with acyl chloride to acylate and modify the surface, a transparent plastic film with high water vapor barrier properties is laminated on the acylated pVA film side, and the other side is acylated. It is preferable to laminate a transparent plastic film with low water vapor barrier properties on the surface of the PVA film that has not been catalytically modified with the acyl chloride.

In addition, when both sides of the PVA film are brought into contact with acyl chloride to acylate and modify the surface, a transparent plastic with high water vapor barrier properties is added to either side of the PVA film modified by this acylation. It is preferable to laminate the films and laminate a transparent plastic film with low water vapor barrier properties on the other side.

Here, a transparent plastic film with high water vapor barrier properties is defined as a transparent plastic film with a temperature of 4.
Water vapor permeability under conditions of 0°C and 90% relative humidity (hereinafter abbreviated as 40°C x 90% RH) is 2 g/m2
・24 brs, 20μ or less. Such films include polyvinylidene chloride, films made of vinylidene chloride resins such as vinylidene chloride-vinyl chloride copolymers, films made of polytetrafluoroethylene, polypropylene films, polyethylene films, polyethylene terephthalate films, Examples include vinylidene coated film, which is a nylon film coated with vinylidene chloride resin.

Furthermore, a plastic film with low water vapor barrier properties is defined as one with a water vapor permeability of 8g/m2・24t+rs, 20μ or more under the conditions of a temperature of 40℃ and a relative humidity of 90% (40℃ x 90%RH), based on ASTM F372. preferably 12g/+n2・241+rs, 2
A value of 0 μ or more is preferable. For such a film,
Examples include low-density polyethylene film, high-density polyethylene film, polypropylene film, and unstretched ethylene-vinyl acetate copolymer film.

The thickness of the laminated plastic film according to the present invention is preferably selected in the range of 5 to 500μ, preferably 10 to 200μ, particularly preferably 12 It is selected in the range of ~100μ. That is, the thickness of the PVA film and the film laminated thereon are appropriately selected so that the thickness of the plastic film laminate falls within this range.

The laminated plastic film according to the present invention can be used as an airtight bag, a lid for an airtight container, etc. by coating one or both of its surfaces with a substance that improves the heat sealing properties of the film. In some cases,
Particularly suitable. Examples of substances that improve heat sealability include low density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, and ionomer. This is preferably dissolved in a solution and applied to the film surface, or laminated in the form of a thin film.To produce the transparent laminated plastic film according to the present invention, a method of adhesive lamination using an adhesive; Alternatively, a known method such as a coextrusion method may be used. In the case of adhesive lamination using an adhesive, the adhesive dissolved in an organic solvent is usually applied to both sides of the PVA film after it has been brought into contact with an acyl chloride and modified by a roll coating method or other known method, and then After the solvent has been volatilized, a laminating film wound into a roll is unwound and overlaid on the adhesive-applied surface, and the film is laminated by pressing with a roll.

Here, as the adhesive, known adhesives such as urethane adhesive, acrylic adhesive, polyester adhesive, etc. can be used.

The laminated plastic film according to the present invention may be laminated with films having different properties on both sides of a PVA film as described above, or may be used depending on the purpose.

For example, when using a container or a container lid to store solid objects and to isolate the solid objects from the outside air and prevent gases such as oxygen and water vapor from entering, a plastic film with a high water vapor barrier property is used. The surface is placed on the outside, and the plastic surface with low water vapor barrier properties is placed on the inside to contact the stored solid object. On the other hand, when used as a container for storing items with a high moisture content, insulating the item from the outside air, preventing oxygen intrusion, and releasing water vapor, or as a container lid, water vapor barrier properties are required. The plastic film surface with high water vapor barrier property is the inside, and the plastic film with low water vapor barrier property is the outside. By using the film properly depending on the application in this way, the excellent gas barrier properties of the laminated plastic film according to the present invention can be utilized.

"Effects of the Invention" The laminated plastic film according to the present invention has the following particularly remarkable effects, and its industrial utility value is extremely large.

(1) The laminated plastic film according to the present invention has excellent transparency and exhibits extremely excellent gas barrier properties. It is also excellent in terms of bending strength, flexibility, and economy.

(2) The laminated plastic film according to the present invention has a water vapor transmission rate of 1.0 g/
m2・24hrs, 20μ or less, and the oxygen permeability is also 0, 1 cc/m2・24hrs, atII
1 or less, and exhibits excellent gas barrier properties over a long period of time.

(3) The laminated plastic film according to the present invention has the excellent properties listed in -, so it can be used as a packaging material for foods, medicines, chemicals, etc., and as a packaging material that requires a high degree of gas barrier property. As such, it is extremely useful.

"Examples" The present invention will be specifically explained below with reference to Examples.
The present invention is not limited to the following examples unless the scope thereof is exceeded. Comparative examples are also included in order to clarify the effects of the present invention.

In addition, in the following examples, the water vapor transmission rate is ASTM
Based on F372, under the conditions of 40°C x 90% RH,
Heat the high water vapor barrier side of the laminate to high temperature (90% RH)
The oxygen permeability was measured using 0X-TRAN 100 manufactured by Modern Control Co., Ltd.
Measured under the conditions of ℃ x 80% RH.

In all examples, the lamination method was a dry lamination method using a urethane adhesive.

The transparency of the laminate was visually observed and evaluated.

Example 1 10 cc of benzoyl chloride (boiling point 197°C) was placed in a plastic Petri dish, and I
I placed W. A polyvinyl alcohol film with a vinyl alcohol content of 99 mol% and a thickness of 18μ stretched 3x3 times was placed over -1- of the petri dish, and the inside of the flask was filled with 1. The flask was heated from the outside to 60° C. for 2 hours while maintaining a vacuum of Torr, and both sides of the PVA film were acylated and modified. After cooling to room temperature, the film was taken out and dried using a vacuum dryer at a vacuum of I Torr and 60° C. for 2 hours to remove residual benzoyl chloride.

A urethane adhesive (a two-component adhesive consisting of Taketack A-606 and Takene A-7, manufactured by Takeda Pharmaceutical Co., Ltd.) was applied to one side of this PVA film, and the solvent was evaporated. Also, a biaxially stretched polypropylene film with a 2μ thick polyvinylidene chloride coating layer (water vapor permeability 2, Og/m2・24hrs, 20μ, stretching ratio 5×5 times, total thickness 20μ, hereinafter referred to as this film) PVDC (abbreviated as OPP) was laminated.

In addition, an unstretched low-density polyethylene film (water vapor permeability 24 (g/m"・24hrs
, 20 /j, thickness 20μ, hereinafter this film is LDP
(abbreviated as E) were laminated.

For the laminated plastic film prepared as above, the PVDC coated OPP surface was heated to high humidity (90% RH).
The water vapor transmission rate was measured with the LDPE side and the LDPE surface placed on the bone-dry side, respectively. Further, the oxygen permeability was measured with the PVDC-coated OPP side placed on the high temperature (80% RH) side and the LDPE side placed on the bone-dry side. The results are shown in Table 1 together with the transparency evaluation results.

Example 2 Polyvinyl alcohol content 99 mol%, 3X
A polyvinyl alcohol film with a thickness of 18 μm stretched three times was immersed in benzoyl chloride at room temperature for 1 hour to acylate both sides of the film and modify it. Then, I
Vacuum dry at 60°C for 2 hours at Torr vacuum.
The remaining benzoyl chloride was removed. Films of the same type were laminated on both sides of this PVA film in the same manner as in Example 1 to obtain a laminated plastic film. This laminated plastic film was also evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3 A laminated plastic film was obtained in the same manner as in Example 2, except that benzoyl chloride in the example described in Example 2 was replaced with 7nameyl chloride. This laminated plastic film was also evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4 In the example described in Example 1, an ethylene-vinyl alcohol copolymer film (hereinafter abbreviated as EVOH) with a thickness of 18μ was obtained by stretching the PVA film 3×3 times with a polyvinyl alcohol content of 70 mol%. A laminated plastic film was obtained in the same manner as in Example 1, except that

This laminated plastic film was also evaluated in the same manner as in Example 1. The results are shown in Table @1.

Example 5 A PVA film obtained by treating with benzoyl chloride in the same manner as in Example 1 was coated with a PVDC film on one side.
opp, and a biaxially stretched polypropylene film (water vapor transmission rate 8g/+n2・241+rs, 2
0μ, stretching ratio 5×5 times, thickness 20μ.

This film is hereinafter abbreviated as OPP) was laminated in the same manner as in Example 1 to obtain a laminated plastic film. Regarding this laminated plastic film,
The same evaluation as in Example 1 was performed.

The results are shown in Table 1.

Example 6 One side of a PVA film obtained by treatment with benzoyl chloride in the same manner as in Example 1 was coated with PDC Co) O.
PP, and an ethylene-vinyl acetate copolymer film with a vinyl acetate content of 5 mol% (water vapor permeability 5
(0g/m2.24hrs, 20μ, thickness 20μ, hereinafter this film will be abbreviated as EVA) were laminated in the same manner as in Example 1 to obtain a laminated plastic film. This laminated plastic film was also evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 In the example described in Example 1, EVO with a polyvinyl alcohol content of 40 mol% was used instead of the P XI A film.
H film (stretched 3x3 times, thickness 18μ)
A laminated plastic film was obtained in the same manner as in Example 1, except that a plastic film was used. This laminated plastic film was also evaluated in the same manner as in Example 1. The results are also listed in Table 1.

Comparative Example 2 A PVA film obtained by treating with benzoyl chloride in the same manner as in Example 1 was laminated with OPP on one side and LDPE on the other side in the same manner as in Example 1. A plastic film was obtained. This laminated plastic film was also evaluated in the same manner as in Example 1.

The results are also listed in Table 1.

Comparative Example 3 PVDC foot o was applied to both sides of a PVA film obtained by treating with benzoyl chloride in the same manner as in Example 1.
pp to 8! in the same manner as in Example 1. A laminated plastic film was obtained. This laminated plastic film was also evaluated in the same manner as in Example 1.

The results are also listed in Table 1.

Comparative Example 4 OPP was laminated on both sides of an aluminum foil with a U-size of 7μ in the same manner as in Example 1 to obtain a laminate. This laminate was also evaluated in the same manner as in Example 1. The results are also listed in Table 1.

℃ ・Residence 1 Out/l.

From Table 1, the following becomes clear.

(1) The laminated plastic film according to the present invention has excellent transparency and extremely excellent gas barrier properties.

(2) The PVA film serving as the center layer of the laminated plastic film according to the present invention needs to have a polyvinyl alcohol content of 50 mol % or more. If the amount is less than this, the gas barrier properties of the obtained laminated plastic film will deteriorate (Comparative Example 1).

(3) In the laminated plastic film according to the present invention, the film laminated after being modified by contact with acyl chloride has a plastic film with high water vapor barrier properties on either the contact surface or the contact surface. ,
It is important that the other film is a plastic film with low water vapor barrier properties, and the gas barrier property of the obtained laminate with either one is insufficient (Comparative Example 2.3).

Claims (4)

[Claims] (1) After at least one side of a polyvinyl alcohol-based plastic film containing 50 mol% or more of polyvinyl alcohol is brought into contact with an acyl chloride compound and modified, a transparent plastic film other than the above film is laminated on both sides of the film. A transparent laminated plastic film with excellent gas barrier properties. (2) A transparent plastic film with high water vapor barrier properties is laminated on the surface of the polyvinyl alcohol-based plastic film that has been catalytically modified with an acyl chloride compound, or on either of the catalytically modified surfaces, and the other Claims (1) characterized in that the surface is laminated with a transparent plastic film with low water vapor barrier properties.
The transparent laminated plastic film with excellent gas barrier properties as described in 1). (3) A transparent plastic film with high water vapor barrier properties has a water vapor transmission rate of 2 g/m^2.24 hrs. under conditions of a temperature of 40°C and a relative humidity of 90%. Claims (1) to (2), characterized in that the material is selected from those of 20μ or less,
A transparent laminated plastic film with excellent gas barrier properties. (4) A transparent plastic film with low water vapor barrier properties has a water vapor transmission rate of 8 g/m^2.24 hrs. under conditions of a temperature of 40°C and a relative humidity of 90%. The transparent laminated plastic film with excellent gas barrier properties according to any one of claims (1) to (3), characterized in that the film is selected from those with a diameter of 20μ or more.